In the prior art, either when heat sealing the side and bottom seams of a frustoconical two-piece cup, for example, or when gluing these same seam areas in such a container, a mandrel having a movable tip has been utilized in the fabricating apparatus to selectively apply pressure to the seams and a point of reference to the bottom blank during the cup forming process to maintain it in place for the final sealing pressure to be applied thereto. The mandrels either have a solid plunger which reciprocates in and out of a hollow tip or have a solid extensible tip portion on the mandrel, either system being disadvantageous. In the case of the hollow tipped mandrels, such hollow tips or nose pieces are very vulnerable to damage and are expensive to manufacture. Furthermore, they are subject to discontinuities in the edges thereof which tend to cut through the thermoplastic coatings on the paperboard or otherwise disfigure or cut the material from which the two-piece cup is being made thereby causing areas of weakness and the potential for leaks in the side seam.
The solid mandrel or plunger types which utilize extendable tip portions create a stepped area (discontinuity) in the side seam just above the bottom wall of the cup or container which must be ironed out or compensated for such as by a stepped configuration in the conventional side seam clamps which are utilized to effectuate the side seam seal and therefore, this discontinuity is another source of quality control problems such as leaks and weakness.
It is therefore an object of the present invention to provide new and novel mandrel structures for sealing the side and bottom seams of conventional two-piece cups and the like by leak sealing or gluing.
Still another object of the present invention is to provide new and novel methods and apparatus for heat sealing and gluing the side and bottom seams of a two-piece conventional cup or the like.
Yet another object of the present invention is to provide a new and novel method and apparatus for heat sealing thermoplastic coated two-piece paperboard containers in the side and bottom seam areas.
These and other objects of the present invention will become more fully apparent with reference to the following specification and drawings which relate to several preferred embodiments thereof.